Multiple string replacements (within the same string)

Question

I have a string. For simplicity it could look like this:

\r\n\r\n\r\n

It could also have more occurrences '\r\n' - I'm only posting the simplest problem here.

I need to insert a space between each occurrence of '\r\n\r\n' For the example above, I expect to end up with a string that looks like:

\r\n \r\n \r\n

I CAN do this using the following code (which I don't like because it creates a lot of strings in order to produce the expected result):

string newString = "\r\n\r\n\r\n";
while (newString.Contains("\r\n\r\n"))
      newString = newString.Replace("\r\n\r\n", "\r\n \r\n");

I have had problems trying to use string.Replace or figure out a regular expression that can do this for me.

If I try to use string.replace (or even a StringBuilder.Replace) like so...

var result = "\r\n\r\n\r\n".Replace("\r\n\r\n", "\r\n \r\n");

I end up with

"\r\n \r\n\r\n"  //There is no space between the last two carriage return / line feed

I think that a regex replace could do the trick, but I can't figure out how to get the regex engine to do a lazy match in order to replace all occurrences of \r\n after the first replace.

I have been searching both SO and google trying to find a similar problem, but haven't turned up anything of use. I apologise in advance if this is a duplicate, but if it is, I can't find it!

So in summary, I can do this using the while loop, but I wanted to know if there was a more elegant solution?

EDIT

Sorry - there is a bit more to this: My code may also review a string that looks like this:

5\r\n\r\nTest\r\n

In which case, I would expect to see a string that looks like this:

5\r\n \r\nTest\r\n

So - I don't want to just replace '\r\n' with '\r\n ' as this would give me a string that looks lke:

"5\r\n \r\n Test\t\n "

Can you try newString = newString.Replace("\r\n", "\r\n ").Trim(); ? — Dieter B
– Dieter B, Commented Apr 6, 2016 at 12:02
Sorry - added more detail as I realised I had omitted an important part of my question. — Jay
– Jay, Commented Apr 6, 2016 at 12:09

juharr · Accepted Answer · 2016-04-06 12:11:53Z

4

You can use a look ahead and look behind so that you only match the "between" part.

string test = "\r\n\r\n\r\n";
Regex reg = new Regex("(?<=\r\n)(?=\r\n)");
test = reg.Replace(test, " ");

That will result in test being "\r\n \r\n \r\n".

edited Apr 6, 2016 at 12:11

answered Apr 6, 2016 at 12:06

juharr

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1 Comment

Jay Over a year ago

Just plugged this baby into my unit test and it passed first time... thanks!

Kajal · Accepted Answer · 2016-04-06 12:08:21Z

-1

"\r\n\r\n\r\n".Replace("\n\r", "\n \r");

answered Apr 6, 2016 at 12:08

Kajal

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3 Comments

Jay Over a year ago

Sorry - please see my edit on the qquestion - this is not what I am trying to do

juharr Over a year ago

This is over simplifying. A string like "\n\r" should not get a space inserted based on the OP's requirements.

Nikolay Fedorov Over a year ago

Juharr, "\n\r" may use as variable. This is just example.

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